Today there exists a vast number of tractor-trailers which are used to transport freight in the trucking industry. Many of these trailers are refrigerated in order to be used to transport perishable goods. Refrigerated trailers typically have a refrigeration unit mounted to the front of the trailer. The refrigeration unit houses a refrigeration system that typically includes a small diesel engine which continuously or cyclically powers a heat exchanger in the refrigeration system.
In cold weather the freight contained within a trailer may be required to be kept warmer than the ambient temperature. For this reason, the heat exchanger, typically in the form of a heat pump, can be operated in a reverse thermodynamic cycle so as to supply warmed air to the interior of the trailer upon demand. The heat pump is also used in reverse cycle to melt ice which accumulates on the evaporator coils during a refrigeration cycle. The heat pump thereby defrosts the refrigeration system. During the defrost operations a damper prevents the warm air from entering the trailer.
The tractor also usually has a climate control system itself for controlling the temperature of the air within the cabin for the benefit of the driver. The climate control system of the tractor is comprised of both a refrigeration system and a heating system. Each system is driven by the tractor engine. The incremental energy to operate these systems is low while the engine is used to drive the tractor-trailer. However, oftentimes drivers rest or sleep in the cabin with the tractor-trailer parked. Should a driver wish to operate either one of the tractor's climate control systems during this rest period, the tractor engine must be operated merely to drive the climate control system. This results is an increase in fuel consumption which is wasteful, because even at idle the tractor engine produces far more power than is necessary to drive the cabin climate control systems.
An effort has heretofore been made to solve this problem by tapping into the refrigeration system of the trailer as shown in U.S. Pat. No. 3,211,076. However, as this system does not provide warm air to the cabin, the engine of the tractor must still be operated in order to warm the cabin in cold weather. This system also cannot cool the cabin when the heat exchanger is operated in a reverse thermodynamic cycle.
Accordingly, it is seen that a need remains for a climate control system which selectively provides cooled or warmed air to the cabin of a tractor-trailer having a trailer refrigeration system. Accordingly, it is to the provision of such that the present invention is primarily directed.